Researchers at Stanford University conducted experiments that show targets of bias are more likely speak up if they believe people's personalities can change.

The study, published in one of the Association for Psychological Science's journals, Psychological Science, found the same is true whether the biased remark made to participants was communicated lightly or blatantly.

In one experiment, Stanford students, who were ethnic minorities and/or female, were told they had to discuss college admissions with another student via instant message.

That other student, actually a researcher, was a white sophomore named Matt. "Matt" indicated he thought he had to be overqualified for college "because of the whole diversity admissions thing--so many schools reserve admissions for students who don't really qualify the same way."

Study participants could choose whether to respond or not. Those who did tended to believe they could change Matt's mind.

More details about the study can be found here.